This puzzle:

Notepad: When this puzzle is done, the answers will include a familiar series of 38-Across (minus the middle square). Connect the squares of this series in order with a line, starting with the circled square. The resulting image will be a pair of 38-Across (WITH the middle square). In addition, the clues all share a feature that provides an additional hint to the puzzle's theme.

JimH notes: There are EIGHT NOTES that, when connected in order, form a pair of EIGHTH NOTES. Also, every clue starts with a solfège name: Do, Re, Mi, etc.